Thread: new 350 overheating

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Casting # will tell you which rotation it has. Get the casting # and google it. Or you remove the pump, take the back cover off and look at the direction the vanes go. As the housings are the same and only the impeller design is different you wont be able tell from the outside, only with the casting #. On some aftermarket pumps there is a little arrow cast into the pump casing to show the direction of rotation. I think not on stock pumps.

Just read your first post again: If it pressurizes quickly and the T-stat is OK, then it's quite a sure sign of the wrong rotation if all other things are OK. Pressure at first should go into the block, but with a closed T-stat it should stay in the engine and not get into the rad yet. Only when the T-stat opens it should pressurize the whole cooling system. Where exactly do you measure temp and pressure?

And did you measure the ring gaps before installing? No waterpump can cool butting rings... (But on the other hand, butting rings would have killed your engine by now probably...)

Oil pump and oil pressure checked?
Non-standard friction will overheat your engine quite quickly.